President Felipe Calderón has said he is willing to change Mexico's drug-war strategy and promised a new offensive against money laundering after hearing blistering criticism from opposition leaders.

Calderón's drug-war talks, the latest session with leaders of the country's opposition political parties, comes as the government offensive against drug cartels draws more criticism. More than 28,000 people have died in drug-related violence since Calderón launched his offensive in late 2006, sending thousands of troops to drug hotspots.

"I know that the strategy has been questioned, and my administration is more than willing to revise, strengthen or change it if needed," Calderón said at the meeting. "What I ask, simply, is for clear ideas and precise proposals on how to improve this strategy."

The series of meetings started last week with Calderón calling together academics, experts and civic groups to exchange ideas on combating drugs.

For more than three-and-a-half years, Calderón fiercely defended his policies, even as vicious cartel turf battles and attacks on police spread deep into Mexico and along the regions bordering the US.

He now appears more willing to discuss alternatives – even the legalisation of drugs, a proposal he has opposed. Calderón repeated his argument again: that unilateral legalisation would increase drug use and do little to reduce the cartels' income.

The toughest criticism from opposition leaders came on the subject of money laundering. An estimated $10bn (£6bn) in suspicious cash, possibly linked to drug trafficking, flows through Mexico annually, fuelling the cartels' violence and ability to bribe officials.

"The government's strategy is not working," said Jesus Ortega, leader of the leftist Democratic Revolution Party. "I don't think there even is a strategy … a government policy implies attacking this financial system that benefits from money laundering, and as a consequence, benefits from the violence."

While Mexico imposed tough restrictions on US dollar transactions in June, limiting tourists and Mexicans without bank accounts to exchanging a maximum of $1,500 in cash each month, critics claim little has been done to combat laundering through banks or other businesses.

"This money – millions and millions of dollars – isn't stuffed under the mattress of the drug lords or the hitmen," Ortega said. "The largest part of this money, the immense majority, is in the banks and financial institutions of Mexico and the United States."

Calderón says officials from Mexico's treasury and central bank are drawing up a new strategy to fight money laundering.

"I have asked that this be presented this week," Calderón said, but did not offer specific details.

Earlier this month the Mexican Banking Association proposed that the government impose limits on cash transactions in pesos as well as dollars.

The association's vice president, Luis Peña, proposed at the time that transactions conducted in cash be limited to about 50,000 pesos (£2,400).

Calderón said Mexico has had a hard time hiring the kind of financial experts needed to fight money laundering, because wages in the private sector are higher and the risks of government service are greater.

Other political leaders at the meeting said the government needs to do more to provide educational and job opportunities for young people who otherwise might lapse into drug addiction, or be recruited by drug cartels.

Yesterday Mexican troops detained seven people counting more than 16 million pesos in cash at a home in northern Mexico and a gunman who was guarding the house, the defence department said.

The department said the gunman ran inside the house in the Monterrey suburb of Guadalupe after seeing the soldiers, who gave chase and found the other suspects.